I have both programs. ActiveSky6 is a weather engine - you can download current weather to fly in and it'll update continuously throughout your flight. ActiveSky6 also includes Graphics that have great looking clouds and weather visuals. One feature that's particularly nice is that it'll produce weather effects based on the specifics of the station wx. Flight Environment is a set of add-on clouds, sunrise, sunsets, water textures, etc. that looks great as well. In fact, it's possible to use Flight Environment effects with the ActiveSky downloaded weather. I did this for awhile, but have found ActiveSky's graphics to be so good that I use ActiveSky exclusively now. If I were to choose just one of the programs today, it would be ActiveSky because of it's weather engine and consider the graphics a GREAT included bonus. Hope that helps!